Cyclists travel on the road on a hazy day in Huaibei, in central China's Anhui province Monday Jan. 14, 2013. Air pollution is a major problem in China due to the country's rapid pace of industrialization, reliance on coal power, explosive growth in car ownership and disregard for environmental laws. (AP Photo) CHINA OUT less

Cyclists travel on the road on a hazy day in Huaibei, in central China's Anhui province Monday Jan. 14, 2013. Air pollution is a major problem in China due to the country's rapid pace of industrialization, ... more

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Retirees play Taichi during their morning exercise on a hazy day in Fuyang city, in central China's Anhui province, Monday Jan. 14, 2013. Air pollution is a major problem in China due to the country's rapid pace of industrialization, reliance on coal power, explosive growth in car ownership and disregard for environmental laws. (AP Photo) CHINA OUT less

Retirees play Taichi during their morning exercise on a hazy day in Fuyang city, in central China's Anhui province, Monday Jan. 14, 2013. Air pollution is a major problem in China due to the country's rapid ... more

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People visit a park near the Military Museum, seen in background, on a hazy day in Beijing, China, Monday, Jan. 14, 2013. Beijing schools kept children indoors and hospitals saw a spike in respiratory cases Monday following a weekend of off-the charts pollution in China's smoggy capital, the worst since the government began being more open about air-quality data. (AP Photo/Alexander F. Yuan) less

People visit a park near the Military Museum, seen in background, on a hazy day in Beijing, China, Monday, Jan. 14, 2013. Beijing schools kept children indoors and hospitals saw a spike in respiratory cases ... more

Photo: Alexander F. Yuan

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A man walks on an frozen lake on a hazy day in Beijing, China, Monday, Jan. 14, 2013. Beijing schools kept children indoors and hospitals saw a spike in respiratory cases Monday following a weekend of off-the charts pollution in China's smoggy capital, the worst since the government began being more open about air-quality data. (AP Photo/Alexander F. Yuan) less

A man walks on an frozen lake on a hazy day in Beijing, China, Monday, Jan. 14, 2013. Beijing schools kept children indoors and hospitals saw a spike in respiratory cases Monday following a weekend of off-the ... more

Photo: Alexander F. Yuan

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Severe Beijing smog prompts unusual transparency

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BEIJING — One of Beijing's worst rounds of air pollution kept schoolchildren indoors and sent coughing residents to hospitals Monday, but this time something was different about the murky haze: the government's transparency in talking about it.

While welcomed by residents and environmentalists, Beijing's new openness about smog also put more pressure on the government to address underlying causes, including a lag in efforts to expand Western-style emissions limits to all of the vehicles in Beijing's notoriously thick traffic.

Even state-run media gave the smog remarkably critical and prominent play. "More suffocating than the haze is the weakness in response," read the headline of a front-page commentary by the Communist Party-run China Youth Daily.

Government officials — who have played down past periods of heavy smog — held news conferences and posted messages on microblogs discussing the pollution.

The wave of pollution peaked Saturday with off-the-charts levels that shrouded Beijing's skyscrapers in thick gray haze. Expected to last through Tuesday, it was the severest smog since the government began releasing figures on PM2.5 particles — among the worst pollutants — early last year in response to a public outcry.